Controlling exhaust temperatures

ABSTRACT

An exhaust manifold cooling jacket has internal passages for the circulation of liquid coolant and encloses an exhaust manifold such that a gap is created between the exhaust manifold and cooling jacket. Flowing coolant through the jacket regulates outer jacket temperature while enabling high intra-manifold exhaust gas temperatures for thorough intra-manifold combustion and improved emissions. A liquid-cooled exhaust system includes a turbocharger disposed between manifold and elbow, with liquid coolant flowing from manifold to elbow through the turbocharger. Another liquid-cooled exhaust manifold contains an internal exhaust combustion catalyst wrapped in an insulating blanket. In some marine applications, seawater or fresh water coolant is discharged into the exhaust gas stream at an attached exhaust elbow.

This application is a continuation (and claims the benefit of priorityunder 35 USC 120) of U.S. application Ser. No. 12/791,691, filed Jun. 1,2010; which is a continuation of U.S. application Ser. No. 11/557,431,filed Nov. 7, 2006; which is a continuation of U.S. application Ser. No.09/862,973, filed May 22, 2001; which claims priority from U.S.provisional application Ser. No. 60/206,050, filed May 22, 2000. Thedisclosures of the prior applications are considered part of (andincorporated in) the disclosure of this application.

TECHNICAL FIELD

This application claims priority from U.S. Provisional Application No.60/206,050, filed May 22, 2000, which is incorporated herein byreference.

This invention relates to cooling engine exhaust manifolds and relatedcomponents, and more particularly to controlling the temperature ofengine exhaust components and the exhaust gasses flowing through them.

BACKGROUND

The exhaust gasses flowing through an exhaust gas manifold of aninternal combustion engine are typically very hot, and the exhaustmanifold itself may reach very high surface temperatures. To keep theouter surface temperature of the exhaust manifold down for safetyreasons, some exhaust manifolds are water cooled, meaning that theycontain inner passages through which cooling water flows during engineoperation or that they are placed within jackets with cooling waterflowing directly across the outer surface of the manifold. Indeed, thereare some regulations requiring that exhaust manifolds be provided withcooling jackets for particular applications, such as for marine vesselinspections.

SUMMARY

In one aspect, the invention features a cooling jacket having internalpassages for flowing water or other coolant through the jacket tomoderate jacket temperature. The jacket attaches to the engine cylinderhead to enclose and cool the exhaust manifold of the engine, therebymoderating the temperature of the exhaust gas flowing through themanifold and blocking the outer surface of the manifold from unwantedcontact with nearby objects or personnel. As the coolant flows throughinternal passages in the manifold rather than through or across theexhaust manifold, the coolant never comes into contact with the manifolditself. Manifold cooling is achieved via radiant and convective heattransfer to the jacket when an air gap is provided between the outersurfaces of the manifold and the inner surfaces of the cooling jacket,or by conduction through an insulating material placed between themanifold and jacket. Among the various aspects of the invention are thecooling jacket so described, engines equipped with such cooling jackets,and methods of cooling engine exhaust manifolds by incorporating suchjackets.

In some embodiments the cooling jacket defines a coolant inlet and acoolant outlet that are both separate from the exhaust stream. In someother cases, particularly applicable to marine engines, for example,coolant enters the jacket through a separate inlet but then joins theexhaust flow as the exhaust leaves the manifold, thereby furtherreducing exhaust gas temperature.

In another aspect, the invention features a liquid-cooled turbochargerdisposed between a liquid-cooled exhaust manifold and a liquid-cooledexhaust elbow, such that manifold cooling fluid flowing to the elbowflows through and cools the housing containing the turbocharger.Preferably, for marine applications, for instance, the cooling fluid isinjected into the exhaust stream downstream of the turbocharger, such asin the elbow. In some cases, the manifold cooling fluid flows throughthe exhaust manifold itself. In some other cases, the fluid cools themanifold by flowing through a channel within a jacket that surrounds themanifold, as discussed above.

In some embodiments, the manifold houses an exhaust conversion catalyst.The exhaust conversion catalyst is arranged within the exhaust stream,such that the exhaust flows through the catalyst, and is isolated fromthe liquid coolant, which flows around the catalyst. Preferably, theflow of liquid coolant joins the flow of exhaust downstream of thecatalyst. In some embodiments, an insulating blanket is placed betweenthe catalyst and the manifold housing to help to insulate the hotcatalyst from the surrounding housing, thereby promoting exhaustconversion and avoiding excessive external surface temperatures. Theblanket can, in some cases, also help to protect fragile catalysts fromshock damage.

In another aspect of the invention, a liquid-cooled exhaust manifoldhouses an exhaust conversion catalyst arranged within the exhauststream, such that the exhaust flows through the catalyst, and isisolated from the liquid coolant, which flows around the catalyst. Themanifold is adapted to receive and join separate flows of exhaust gasand direct them through the catalyst. The manifold comprises a one-piecehousing, preferably of cast metal, forming the internal exhaust flowpassages and cavity for receiving the catalyst.

Some aspects of the invention can provide for the ready modification ofengines to comply with exhaust manifold cooling requirements, withouthaving to modify the exhaust manifold to either provide for internalcooling or withstand prolonged surface contact with a desired coolant.Furthermore, the temperature of the exhaust gas within the manifold canbe maintained at a higher temperature than with normally cooledmanifolds, given a maximum allowable exposed surface temperature,enabling more complete intra-manifold combustion and improving overallemissions. Among other advantages, some aspects of the invention help tomaintain high exhaust temperatures, such as to promote exhaust catalyticconversion, for example, without producing undesirably high externalsurface temperatures.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

DESCRIPTION OF DRAWINGS

FIGS. 1A and 1B are front and back perspective views, respectively, ofan exhaust manifold cooling jacket.

FIG. 2 is a side view of the cooling jacket, viewed from the sideadjacent the engine.

FIG. 3 is an end view of the cooling jacket.

FIGS. 4 and 5 are cross-sectional views, taken along lines 4-4 and 5-5,respectively, in FIG. 2.

FIG. 6 is a cross-sectional view, taken along line 6-6 in FIG. 3.

FIG. 7 is a perspective view of a mounting plate for the cooling jacket.

FIGS. 8A and 8B are front and back perspective views, respectively, ofan exhaust elbow.

FIG. 9 is an end view of the exhaust elbow, as looking toward thecooling jacket.

FIG. 10 is a side view of the exhaust elbow.

FIGS. 11 and 12 are cross-sectional views, taken along lines 11-11 and12-12, respectively, in FIG. 9.

FIG. 13 is a cross-sectional view, taken along line 13-13 in FIG. 10.

FIG. 14 is a perspective view of a liquid-cooled exhaust manifold sizedto house a catalytic conversion element.

FIGS. 15 and 16 are end and side views, respectively, of the manifold ofFIG. 14.

FIGS. 17 and 18 are cross-sectional views, taken along lines 17-17 and18-18, respectively, in FIG. 16.

FIG. 19 is a cross-sectional view, taken along line 19-19 in FIG. 18.

FIG. 20 is a top view of a liquid-cooled exhaust system including amanifold, turbocharger, and injection elbow.

FIG. 21 is an exploded perspective view of the exhaust system of FIG.20.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

Referring first to FIGS. 1A and 1B, cooling jacket 20 is sand orinvestment cast in a shape designed to form an interior cavity 22 sizedto fit about an engine exhaust manifold (not shown) when the coolingjacket is mounted against the engine head. In this embodiment, thejacket includes a mounting boss 24 and associated exhaust port 26through which exhaust gas flows from the manifold to a downstreamexhaust elbow (shown in FIGS. 8A through 13). Accordingly, boss 24features mounting holes 28 through which fasteners from the exhaustelbow extend into threaded bosses on the exhaust manifold, sandwichingthe cooling jacket 20 between the manifold and elbow and sealing theexhaust passage. If desired, the cooling jacket may also be mountedsecurely to the engine cylinder head by appropriate lugs and fasteners(not shown).

Referring also to FIGS. 2-6, cooling jacket 20 is cast to define aninternal cooling passage or cavity 30 in hydraulic communication with acoolant inlet 32, which is attached to a pressurized coolant source (notshown) for circulating coolant through the cooling jacket. From passage30, the coolant exits the cooling jacket through ports 34 in boss 24 andflows into the exhaust elbow, where it is blended with the exhaust gas.Alternatively, a separate coolant exit port (not shown) may be providedfor returning the coolant to its source.

As shown in FIG. 3, in this embodiment an air gap 31 is formed betweenthe inner surface of the cooling jacket and the outer surface 33 of theexhaust manifold (shown in dashed outline). Alternatively, anappropriate insulating material, such as glass fiber (not shown), may bepacked into this gap and provide insulation against heat conductionbetween the exhaust manifold and cooling jacket.

Cooling jacket 20 may be cast of any material suitable to the intendedenvironment. For marine applications employing salt water as coolant, asalt resistant aluminum alloy is appropriate. If the cooling jacket isto be mounted directly against a cast iron engine head, or if very hightemperatures are anticipated, cast iron may be more appropriate. Ifaluminum is used and exiting exhaust gas temperatures are high or theexhaust gas is particularly corrosive to aluminum, an iron sleeve may beprovided through exhaust port 26.

To completely enclose the exhaust manifold, a backing plate 36 may beemployed as shown in FIG. 3, and illustrated in FIG. 7. The backingplate is made of flat metal stock, with appropriate exhaust ports placedto align with the exhaust ports of the engine cylinder head. Backingplate 36 is positioned as if it were an exhaust manifold gasket, betweenthe cylinder head and manifold, with the manifold fasteners securing thebacking plate in place. The outer edges of the backing plate engage therim of the cooling jacket, such that there is no appreciable convectiveair flow through the cooling jacket.

Referring now to FIGS. 8A and 8B, exhaust elbow 38 is adapted to mounton boss 24 of cooling jacket 20 (see FIG. 1A) via an appropriatemounting flange 40. Exhaust inlet 42 aligns with exhaust port 26 of thecooling jacket (FIG. 1A), and appropriately positioned coolant inlets 44align with the coolant outlet ports 34 of the cooling jacket (FIG. 1A),such that both the exhaust gasses and coolant enters exhaust elbow 38separately. At its downstream end 46, the exhaust elbow is coupled tothe remainder of the exhaust system (not shown) in typical fashion.

Referring to FIGS. 9-13, from mounting flange 40 and inlet 42 theexhaust gas flows straight through the exhaust elbow along a centralexhaust passage 49 to an exhaust outlet 48. The coolant flows throughcoolant passage 50 to the downstream end 46 of the exhaust elbow, whereit exits the exhaust elbow at outlets 52 and joins the flow of exhaustgas. Coolant passage 50 is not completely annular at either end of theexhaust tube, due to the structural ribs required between the inner andouter portions of the exhaust elbow.

Referring next to FIGS. 14-16, liquid-cooled manifold 54 is produced asa one-piece casting and is designed to merge the exhaust flows fromthree separate combustion cylinders (not shown) entering the manifoldthrough three respective inlets 56. The merged exhaust flows exit themanifold through exit 58, after having passed through a catalyticconversion element contained within the manifold (discussed furtherbelow). Cooling liquid (e.g., fresh water or sea water) enters themanifold through port 60 and exits through port 62.

As shown in FIGS. 17-19, the manifold housing defines coolant passages64 extending about the internal exhaust cavity 66, for circulatingliquid coolant through the manifold to control manifold housing surfacetemperature. Shown disposed within the housing just upstream of exhaustexit 58 in FIG. 17 is a catalytic conversion element 68 surrounded by aninsulator 70. Element 68 is a cylindrical, porous material designed topromote combustion of combustible exhaust gasses. Such materials arewell known in the art of exhaust system design, and a suitable materialis available from Allied Signal as their part number 38972. Element 68has a reasonable porosity and size, at 600 cells per square inch, 3.0inches in diameter and 2.6 inches in length, to perform its intendedfunction without creating excessive exhaust back pressure. Insulator 70is a rolled sheet of vermiculite, having a nominal uncrushed thicknessof about 5 millimeters. Together, catalytic conversion element 68 andinsulator 70 completely span exhaust exit 58, such that all exhaust gasentering manifold 54 is forced to flow through element 68 before exitingthe manifold. By disposing the conversion catalyst within the manifolditself, relatively close to the exhaust source, the high temperaturesdeveloped by secondary combustion are safely contained within aliquid-cooled housing so as to not present any exposed high temperaturesurfaces. As shown in FIG. 17, a major length of catalytic element 68 issubstantially surrounded by coolant passage 64.

Although not specifically illustrated, it should be understood from theabove disclosure that another advantageous arrangement is to house anappropriately sized catalytic conversion element, such as element 68,within a manifold not adapted to circulate cooling fluid, and thensurrounding the manifold with a secondary cooling jacket such as thatshown in FIGS. 1-6. It should also be understood that manifold 54 may bemodified to provide the coolant exit coaxially with the exhaust exit,such that the exiting coolant flows directly into an injection elbow orother downstream exhaust component.

Referring now to FIGS. 20 and 21, liquid-cooled exhaust system 72includes a liquid-cooled exhaust manifold 74, a liquid-cooledturbocharger 76, and a coolant injection elbow 78. The individualexhaust system components are shown separated in FIG. 21. Manifold 74 isconfigured to receive the exhaust from a bank of six combustioncylinders through exhaust inlets 80, and a flow of coolant throughcoolant inlet 82. From manifold 74, both the combined exhaust stream andthe liquid coolant pass directly into the housing of turbocharger 76through ports 84 and 86, respectively. The passed coolant helps tocontrol the surface temperature of turbocharger 76, which uses kineticflow energy from the exhaust gas to boost the pressure of intake air forcombustion in the associated engine. Turbocharger 76 accepts atmosphericair through intake 88 and supplies pressurized air to the engine via airoutlet 90. From turbocharger 76, both the exhaust stream and the liquidcoolant flow directly into injection elbow 78, through ports 92 and 94,respectively. In elbow 78 the coolant is injected into the stream ofexhaust to further cool the exhaust. The placement of turbocharger 76immediately downstream of manifold 74, before the exhaust stream hasexperienced substantial flow losses, promotes turbocharging efficiency.In addition, flowing the coolant through the turbocharger helps tomaintain desirable external turbocharger housing surface temperatures insystems employing downstream water injection, such as for marineapplications. It should be understood from the above disclosure that anyof the three components shown in FIG. 21 may be equipped with aninternal catalytic conversion element, such as element 68 of FIG. 17,and that manifold 74 may be replaced with a standard manifold withoutinternal coolant channels but rather surrounded by a cooled jacket suchas the one shown in FIGS. 1-6.

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention. Forexample, a single manifold/jacket assembly may replace the standardexhaust manifold and contain both internal exhaust passages and internalcoolant passages, with an internal air space between the coolantpassages and exhaust passages such that many of the benefits of theinvention are achieved. Because of direct exposure to high temperatureexhaust gasses, however, such a combination version would be limited toparticular materials, such as cast iron or steel. Accordingly, otherembodiments are within the scope of the following claims.

What is claimed is:
 1. A marine engine exhaust system defining anexhaust passage extending from an engine exhaust manifold inlet to anexhaust system outlet, the exhaust system comprising: an exhaustmanifold configured to merge multiple exhaust flows into a mergedexhaust flow, the exhaust manifold configured to be coupled to an enginecylinder head; and a catalytic conversion element arranged to interceptand catalyze the merged exhaust flow, the exhaust system defining aseawater inlet upstream of the catalytic conversion element, and a rawwater coolant passage extending from the seawater inlet, through theexhaust manifold, between the catalytic conversion element and anadjacent external manifold surface; wherein the raw water coolantpassage is spaced from the engine cylinder head; wherein the raw watercoolant passage extends to a raw water coolant exit open to the exhaustpassage downstream of the catalytic conversion element, such thatseawater is injected into the exhaust within the exhaust system.
 2. Themarine engine exhaust system of claim 1 wherein the seawater inlet isdefined by the manifold and spaced from the engine, such that duringoperation water enters the manifold away from the engine cylinder head.3. The marine engine exhaust system of claim 1 wherein the catalyticconversion element is disposed within the manifold.
 4. The marine engineexhaust system of claim 3 further comprising an insulator separating thecatalytic conversion element from an inner surface of the manifold. 5.The marine engine exhaust system of claim 1 wherein a major length ofthe catalytic conversion element is substantially surrounded by the rawwater coolant passage.
 6. The marine engine exhaust system of claim 1wherein the raw water coolant passage extends along opposite sides ofthe catalytic conversion element.
 7. The marine engine exhaust manifoldof claim 1 further comprising a seawater injection elbow mounteddownstream of the catalytic conversion element and configured to injectthe seawater into the exhaust flow.
 8. The marine engine exhaust systemof claim 1 wherein the catalytic conversion element is disposed adjacenta merging of the multiple exhaust flows.